Supercapacitors (also known as ultracapacitors) store electricity by physically separating positive and negative
charges—unlike batteries which do so chemically. The charge they hold is like
the static electricity that can build up on a balloon, but is much greater
thanks to the extremely high surface area of their interior materials.
Super capacitors are very good at efficiently capturing electricity from
regenerative braking, and can deliver power for acceleration just as quickly.
With no moving parts, they also have a very long lifespan—probably longer than
any car.
A super capacitor is also known as a double-layer capacitor.
It polarizes an
electrolytic solution to store energy electro statically. Though it is an
electrochemical device, no chemical reactions are involved in its energy storage
mechanism. This mechanism is highly reversible, and allows the ultra capacitor to
be charged and discharged hundreds of thousands of times.
A super capacitor can be viewed as two non reactive porous plates, or
collectors, suspended within an electrolyte, with a voltage potential applied
across the collectors. In an individual supercapacitor cell, the applied
potential on the positive electrode attracts the negative ions in the
electrolyte, while the potential on the negative electrode attracts the positive
ions. A dielectric separator between the two electrodes prevents the charge from
moving between the two electrodes. Diagram 2 depicts an supercapacitor, its
modules, and an supercapacitor cell.
Once the supercapacitor is charged and energy stored, a load (the vehicle's
motor) can use this energy. The amount of energy stored is very large compared
to a standard capacitor because of the enormous surface area created by the
porous carbon electrodes and the small charge separation (10 angstroms) created
by the dielectric separator. However, it stores a much smaller amount of energy
than does a battery. Since the rates of charge and discharge are determined
solely by its physical properties, the ultracapacitor can release energy much
faster (with more power) than a battery that relies on slow chemical reactions.
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